Thermal Resistance Test Research Articles

An Alternative Junction-to-Case Thermal Resistance Test Method for High Power Press-Pack IGBTs

An Alternative Junction-to-Case Thermal Resistance Test Method for High Power Press-Pack IGBTs

Investigating Hot corrosion, CMAS, and Thermal Shock Behaviour of Double-layer YSZ/La2Ce2O7 + YSZ Thermal Barrier Coatings

AbstractIn this work, new double-layer YSZ/La2Ce2O7 (LC) + YSZ coatings were developed using air plasma spraying (APS). The surface of the prepared coatings was relatively smooth and consisted of melted and partially melted areas. Their resistance to hot corrosion, CaO-MgO-Al2O3-SiO2 (CMAS), and thermal shock were examined. YSZ was added to the upper layer to enhance the lanthanum cerate (La2Ce2O7, LC) properties. During the hot corrosion tests, the corrosion salt reacted with the upper layer, and the CeO2 phase and new corrosion products were identified. The main phase was LaVO4, and the secondary phases were CeVO4 and YVO4. SEM confirmed the formation of new, cuboidal-shaped corrosion products. The infiltration of CMAS led to the formation of additional new products: Ca4MgxAl4Si(6-x-γ)O14 and Ca2.8(LaxCe1-x).6(SiO4)O6-4x. SEM revealed CMAS infiltration through the upper layer in the form of islands. Following the thermal shock resistance tests, the upper layer gradually peeled off, and the coating survived 67 cycles. Possible failure mechanisms were identified, and failure was attributed to the spallation of the upper layer from the surface layer by layer. After all tests, the top layer showed partial spalling and delamination. This was mainly caused by the reaction of corrosive salt or CMAS with the top layer, which changed its composition, leading to the formation and propagation of cracks and, ultimately, the separation of part of the upper layer. Peeling of the upper layer through mainly horizontal cracks was observed after hot corrosion, CMAS and thermal shocks. The NiCrAlY bond coat and YSZ interlayer remained undamaged.

Synthesis of low-cost refractory cordierite for solar thermal storage: Characterization of mechanical, thermal and physical stability during thermal shock cycles

To guarantee the efficiency of solar thermal energy production, the thermal storage material must have exceptional resistance to thermal shock to withstand prolonged thermal cycles. In addition, it must have specific properties tailored to the requirements of this field. In this study, we developed a refractory cordierite for solar thermal storage, characterized by very high thermophysical properties, from an initial formulation containing 20 % of abundant clays. The properties of materials sintered at 900 °C, 1000 °C, 1100 °C, 1200 °C and 1250 °C were assessed by a series of analyses including X-ray diffraction (XRD), mass loss, volumetric shrinkage, bulk density, and porosity, scanning electron microscopy (SEM), thermal conductivity, thermal diffusivity, thermal storage capacity, chemical resistance, and mechanical testing. The incorporation of natural clays, rich in sintering aid elements, facilitated the formation of 74 % α-cordierite at 1200 °C and 92 % at 1250 °C, significantly enhancing the material's densification. Materials sintered at 1250 °C and containing 92 % refractory cordierite were subjected to 50 thermal shock cycles from 500 °C to 0 °C. The obtained materials showed excellent mechanical properties, including compressive strength of 398 MPa, low porosity of 0.21 %, density of 2.52 g/cm3, zero mass loss in acidic and basic environments for 30 days, and very high values of heat capacity (3429.80 J/(kg·K)), thermal conductivity (2.08 W/(m·K)) and thermal diffusivity (0.84 mm2/s) at room temperature.

COMPARATIVE EFFECT OF WOODFLOUR AND GRANULATED RICE HUSK ON THE THERMAL INSULATION OF TERMITE HILL CLAY

This research work covered the comparative effect of wood flour (saw dust) and granulated rice husk on the thermal insulation of termite hill clay. The raw clay samples were mined from the Federal University of Technology Akure Campus and processed. Likewise, the saw dust and rice husk were also processed and grinded. The clay samples and the additives were sieved to obtain 300 microns and were mixed in predetermined proportions of 0, 2, 4, 6, 8 and 10 wt. %. Cylindrical samples were developed from the mixtures which were compacted and then air dried before oven dried and finally fired. The fired samples were subjected to selected tests to determine their insulation and refractory properties. These tests include porosity, linear shrinkage, volumetric shrinkage, bulk density, thermalconductivity, thermal shock resistance and cold crushing tests. It was discovered that the saw dust samples meet the ASTM standard for insulating bricks while the rice husk samples did not. Saw dust samples with 2 and 8 wt. % were ones with optimum properties.

Preparing high performance FeAl/Al2O3 coating as tritium permeation barrier

Preparation of tritium permeation barrier (TPB) coating on the surface of structural materials is one of the most effective solutions to solve the issue of tritium permeation in tritium breeder blanket. The FeAl/Al2O3 coating is considered as the most promising candidate material for TPB coating due to its low hydrogen isotopes permeability, good adhesion and excellent radiation resistance. However, the current reported performance of FeAl/Al2O3 coating is much lower than its theoretical value. This work proposed a three-step process to prepare FeAl/Al2O3 TPB coating. By magnetron sputtering deposition, aluminizing and in-situ oxidation, a layer of high quality γ-Al2O3 about 250 nm thick was successfully formed on the 304 stainless steels. The Al2O3 layer was dense and no obvious defects were found. The gas-driven permeation measurements showed that the coating sample had strong ability to inhibit deuterium permeation, where the deuterium permeation flux was reduced by 5 orders of magnitude compared to the uncoated one at 600 °C, which is the best reported performance. Meanwhile, the thermal shock resistance test showed that the coating had no cracks after 50 thermal cycles. Moreover, the coating had a high electrical resistivity of approximately 3.42 × 1014 Ω cm, which could effectively reduce the magneto-hydrodynamic pressure drop (MHD) effects.

Transient temperature measurement of silicon carbide Schottky barrier diode based on thermal reflection.

In this article, we present a transient temperature detection device for silicon carbide (SiC) Schottky barrier diodes (SBDs) based on thermal reflection theory. We constructed a thermal reflection temperature measurement device based on a 530-nm green laser. This device is more suitable for transient temperature measurement of SiC SBDs than previous thermal reflection equipment. The accuracy of temperature measurement by our device was confirmed by comparison with the results of infrared thermal imaging. The high temporal resolution characteristics of the thermal reflection technology allowed the detection of millisecond-level transient temperature changes in SiC SBDs. In addition, we investigated the complementarity of transient temperature change curves during heating and cooling processes, as well as the reasons for the differences between these curves. Finally, we used the structural function method combined with the Bayesian deconvolution algorithm to obtain the thermal resistance along the heat flow path of the device and validated the results using an established thermal resistance testing method.

Synthesis and application of environmental plasticizers based on benzene polyacid ester

AbstractUsing benzene‐1,3,5‐tricarboxylic acid, trimellitic anhydride, 2‐propylheptanol and 2‐ethylhexanol as raw materials, four kinds of environmental plasticizers were prepared, which were used as additives for polyvinyl chloride (PVC) products. Compared with commercially available di (2‐ethylhexyl) phthalate (DOP), di (2‐ethylhexyl) terephthalate (DOTP), and tributyl citrate (TBC), the application performance and plasticizing performance were compared. The structure of the target product was analyzed by fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy to verify the fingerprint region of the molecular structure of the product. The properties of plasticized PVC films were tested by thermal weight loss analysis, oven thermal aging test, migration and volatility resistance test, DMA analysis, and scanning electron microscopy. The plasticizing mechanism was confirmed through quantum chemical calculations, and the results of the calculations were in line with the migration outcomes. The results showed that compared with commercially available plasticizers, benzene polyacid ester plasticizers had better thermal stability, and better cold resistance in the polar environments, suitable for high‐temperature and water‐based environments.Highlights The four plasticizers prepared in this study were compared with reference plasticizers, and the plasticizing mechanism was validated through quantum chemical calculations. The PVC film plasticized with benzene polyacid ester prepared in this study demonstrates outstanding thermal stability, surpassing certain plasticizers reported in current literature. Benzene polyacid esters plasticized PVC film has migration stability under various conditions, it has great potential in packaging and other applications.

Recycling Waste Agricultural Nets as Cement Composites.

The advancement of agricultural mesh technology has contributed to its improved properties. As a result, agricultural nets are widely adopted in large-scale farming applications, for example, in cereal crop farming. However, a consequence of this increased use of agricultural nets is the accumulation of large amounts of waste. The current paper focuses on the recycling of agricultural nets used in wrapping straw bales to develop additives and fillers in cement composites. The research details an analysis of the use of waste agricultural meshes as an ingredient in cement composites. Six test series of different mixtures were conducted. In the first four series, agricultural waste was utilised as an additive in a composite comprising aggregate and cement slurry (the amounts of wasted nets were 20, 40, 60, and 80 kg/m3). In the last test series, the recyclate utilised comprised a mixture of cement slurry and waste only. The composites were subjected to standard tests and thermal resistance tests. The results showcased that that the addition of a net worsened the workability of the concrete mixture, and with increasing amounts of addition, the consistency of the mixture could change from liquid to dense plastic. The flexural strength of the composite decreased with increasing amounts of recyclate. In subsequent test series, the flexural strength value was lower than that of the control (3.93 MPa), from 7.38% (3.64 MPa) for the composite with 20 kg/m3 of recyclate to 37.66% (2.45 MPa) for the composite with of 80 kg/m3 recyclate. The flexural strength value of the net-filled composite without aggregate was very high (10.44 MPa), where the value obtained for the control composite was 62.36% lower. The results of the compressive strength test showed a decrease in this parameter with increasing amounts of additive. The value assessed for the control composite was 27.99 MPa. As expected, the composite that had no aggregate and consisted of only recycled filler had the lowest compressive strength. The value of this parameter was 13.07 MPa, and it was 53.31% lower than that of the control composite. The results of the tests of resistance to temperatures were similar to those recorded for the composites with polypropylene fibres. All composites demonstrated a significant decrease in their compressive and flexural strength after annealing. SEM imaging showed that the net fibres were closely bonded to the cement stone. Finally, it was concluded that recyclates performed best as fillers in lightweight composites with a low density, low absorption, high flexural strength, and satisfactory compressive strength.

Comparison of mechanical and comfort properties of natural fiber-based spacer fabrics for shoe insole

The objective of this study is to develop an improved shoe insole that enhances heat and moisture transmission (thermo-physiological comfort) qualities, as well as its mechanical characteristics, through the utilization of weft knitting spacer fabric. Two samples were prepared. One sample was comprised of Tri-Blend knitted fabric layers, while the other sample was made using cotton knitted fabrics in both layers. These layers, in both samples, were connected by spacer yarns of monofilament nylon. Tri-blend fabric was made from Bamboo (80%), flax (15%), and polypropylene (5%). Monofilament nylon was used in spacer layer. Thermo-physiological comfort testing i.e., air permeability, moisture management and thermal resistance test were performed for all the samples. The investigation also established the correlation between the mechanical properties, such as puncture resistance and tactile comfort, of footwear materials and their interaction with the human body. The prepared samples of shoe insole were also compared with the commercially available insoles made from synthetic materials. The outcome of the study suggests that the natural fiber spacer fabric can be used as an alternative to rubber. In conclusion, the results of this study offer valuable insights for product developers seeking sustainable alternatives that can meet consumer demands for both wearability and comfort.

Soft Robotic Textiles for Adaptive Personal Thermal Management.

Thermal protective textiles are crucial for safeguarding individuals, particularly firefighters and steelworkers, against extreme heat, and for preventing burn injuries. However, traditional firefighting gear suffers from statically fixed thermal insulation properties, potentially resulting in overheating and discomfort in moderate conditions, and insufficient protection in extreme fire events. Herein, an innovative soft robotic textile is developed for dynamically adaptive thermal management, providing superior personal protection and thermal comfort across a spectrum of environmental temperatures. This unique textile features a thermoplastic polyurethane (TPU)-sealed actuation system, embedded with a low boiling point fluid for reversible phase transition, resembling an endoskeleton that triggers an expansion within the textile matrix for enhanced air gap and thermal insulation. The thermal resistance improves automatically from 0.23 to 0.48Km2W-1 by self-actuating under intense heat, exceeding conventional textiles by maintaining over 10°C cooler temperatures. Additionally, the knitted substrate incorporated into the soft actuators can substantially mitigate convective heat transfer, as evidenced by the thermal resistance tests and the temperature mapping derived from numerical simulations. Moreover, it boasts significantly increased moisture permeability. The thermoadaptation and breathability of this durable all-fabric system signify considerable progress in the development of protective clothing with high comfort for dynamic and extreme temperature conditions.

Preliminary small-scaled thermal resistance testing of a masonry wall with enhanced electromagnetic shielding effectiveness

This study presents the preliminary results of a small-scale masonry wall thermal resistance (R-value) measurement. Two small-scale masonry walls were constructed using regular and antimony tin oxide (ATO)-containing bricks. ATO has shown potential for improving the protection against electromagnetic radiation penetration. R-values of the walls were measured using a FluxDAQ device equipped with a heat flux sensor and two temperature sensors for obtaining the heat flux and inside and outside temperatures during the measurement. Furthermore, the thermal conductivity (λ) of the bricks was measured by using the Fox200 Heat Flow Meter. Both results can be used for determining a walls’ thermal transmittance (U-value), which is often used for describing the energy losses and as a measure of a wall's energy efficiency. This research sought to investigate whether there is a correlation between the results obtained by the small-scale masonry wall and Fox200 device. Ultimately, this experiment aims to verify whether the small-scale masonry wall non-standard method described herein can provide approximately similar results to the standardised method.

Thermal and mechanical properties of a sustainable bio-flax fibre-based lightweight aggregate concrete

A novel lightweight aggregate concrete (LWAC) or lightweight concrete (LWC) is developed using expanded perlite powder and lightweight expanded clay aggregate as a replacement for conventional fine and coarse aggregates, respectively. Furthermore, the natural plant-based flax fibre in treated form was added to the LWC mix at three different volume fractions. The mechanical and thermal characterisation of LWC was carried out using the compressive strength test, split tensile test, modulus of rupture, thermal conductivity and thermal resistance test. Moreover, the microstructural and durability properties were obtained using scanning electron microscopy/energy dispersive X-ray spectrum analysis, rapid chloride penetration test, sorptivity test and water absorption test. Test results reveal that the addition of 2.0% flax fibre resulted in improved mechanical, thermal and durability properties when compared to LWC with no fibres. Moreover, the microstructural analysis using SEM revealed the formation of ettringite which is responsible for the strength development in the LWAC mix.

High temperature chlorine corrosion resistance of gradient high entropy alloy coatings prepared by high-velocity-oxygen-fuel spraying

The effect of different gradient structures on the high temperature chlorine corrosion resistance of gradient high entropy alloy coating was studied to improve the service life of the heating surface of a waste-incinerated boiler. NiCrAl ceramic composite coating (NC), high entropy ceramic composite coating (HC), and gradient high entropy alloy coating (TC) were prepared on 12Cr1MoV substrate by high-velocity-oxygen-fuel spraying. The effects of morphology and microstructure of different coatings on thermal shock resistance and high temperature chlorine corrosion resistance were studied. The results indicate that the porosity of NC coating, HC coating, and TC coating decreased in turn. In the thermal shock resistance test from 800°C to room temperature, the average number of thermal shock of TC coating can reach 21. The mass change of TC coating in 650°C high temperature Cl corrosion resistance test is less than 30 mg/cm2 after 50 hours. In summary, the gradient high entropy alloy coating with HEA as the metal bonding phase can improve the density of thermal spraying gradient coating, and enhance the thermal shock resistance and high temperature Cl corrosion resistance of the coating. Based on the comprehensive on-site application results, it can be concluded that the use of high velocity oxygen flame gradient high entropy alloy coating can effectively improve the density, thermal shock resistance, and high temperature Cl corrosion resistance of the thermal spraying gradient coating on the heating surface of the boiler, and has broad application prospects.

Interface Contact Thermal Resistance of Die Attach in High-Power Laser Diode Packages

The reliability of packaged laser diodes is heavily dependent on the quality of the die attach. Even a small void or delamination may result in a sudden increase in junction temperature, eventually leading to failure of the operation. The contact thermal resistance at the interface between the die attach and the heat sink plays a critical role in thermal management of high-power laser diode packages. This paper focuses on the investigation of interface contact thermal resistance of the die attach using thermal transient analysis. The structure function of the heat flow path in the T3ster thermal resistance testing experiment is utilized. By analyzing the structure function of the transient thermal characteristics, it was determined that interface thermal resistance between the chip and solder was 0.38 K/W, while the resistance between solder and heat sink was 0.36 K/W. The simulation and measurement results showed excellent agreement, indicating that it is possible to accurately predict the interface contact area of the die attach in the F-mount packaged single emitter laser diode. Additionally, the proportion of interface contact thermal resistance in the total package thermal resistance can be used to evaluate the quality of the die attach.

The effect of ultrasound on the application properties of organic pigment (red 48:1) and inorganic pigments (lemon yellow and orange yellow lead chromate)

In the recent years, the pigment industry, as a mother industry in the field of color matching, has had many applications and has greatly contributed to the progress of other industries such as textile, dyeing, glazing, construction and industrial paints, compounding, etc. For more optimal use in different industries, paying enough attention to the physical and chemical properties of pigments would be necessary. One of the most effective research projects in this field is the investigation of the effect of ultrasound radiation on the applied properties of pigments. In this research, by irradiating different times of ultrasound on the samples of organic pigment (red 48:1) and inorganic pigments (lemon yellow TL210 and orange yellow TM110 lead chromate) in the aqueous phase, the practical and visible effects were investigated on them. After ultrasonic irradiation on the selected pigments, some color test strips were prepared in a specialized paint laboratory, and they were tested with a spectrophotometer and a graindometer. The results of this research showed the great effect of ultrasound radiation on the reduction of the size of pigment particles and the increase of the opacity and coverage of the pigment, and also the increase of its resistance to sunlight; nevertheless, other properties such as water test, alkaline and acid test and thermal resistance test were not affected by ultrasound. Simultaneous application of dispersant with ultrasound resulted in further improvement of the mentioned properties. Based on the results of this research, paint and pigment companies might use ultrasonic radiation with appropriate probes along with different dispersants in their production line so as to increase production efficiency.

Valorization of ceramic sanitary waste into Resilient phosphoric acid-based geopolymers for sustainable construction: Thermal, mechanical, and microstructural properties

The construction industry's heavy reliance on conventional cement production contributes significantly to global carbon dioxide emissions, prompting the need for eco-friendly building materials. Geopolymers, synthesized from natural materials like clay and fly ash, offer a sustainable alternative to traditional cement. This paper investigates the development of phosphoric acid-activated geopolymers with sanitary ware waste (SWW) as aggregates, aiming to create high-performance, environmentally friendly building materials. Various particle sizes of SWW were incorporated into the geopolymer matrix, revealing a strong relationship between particle size and compressive strength. The inclusion of SWW improved compressive strength, with a notable 83 % increase at 30 % SWW content. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses highlighted the formation of new bonds in the geopolymeric gel, while scanning electron microscopy (SEM) showed microcracks and good adhesion between SWW particles and the geopolymer matrix. Thermal resistance tests demonstrated that SWW-reinforced geopolymers exhibited improved resistance to high temperatures compared to the reference geopolymer. XRD analysis of thermally treated geopolymers revealed the transformation of amorphous phases into stable crystalline phases. SEM/EDX mapping confirmed the presence of silica-rich phases, contributing to the materials' mechanical properties and thermal resistance. This study underscores the potential of SWW-based geopolymers as sustainable, high-performance building materials.

Correlation between in vitro sperm kinetic, oxidative stress assessments and field fertility of cryopreserved bull semen

This study assessed kinetic parameters and oxidative stress in bull sperm after post-thaw (PT) or after sperm selection by Percoll™ gradient, and thermo resistance test (SS + TRT) to identify useful indicators of field fertility. For the experiment, commercial doses of frozen semen were obtained from six Aberdeen Angus bulls. Three of the bulls were classified as high fertility and three as low fertility according to the IFert™ index provided by the international breeding company CRV Lagoa. Pooled semen samples were distributed between two treatment groups for analysis: post-thaw (PT) or sperm selection (SS) (Percoll™) and thermal resistance test (SS + TRT). The samples were evaluated using sperm kinetics (CASA) (motility %, progressive motility %, VCL µm/s, VSL µm/s, VAP µm/s, LIN %, STR % and WOB%), production of reactive oxygen species (ROS), lipid peroxidation, superoxide dismutase (SOD) enzyme activity and total antioxidant capacity. Data were analyzed using Two-Way ANOVA, considering the fertility index, the treatment used in the samples as effects, and the interaction between these factors. When a significant effect was observed, the values were compared using the Bonferroni test. A Pearson Correlation analysis was performed between the fertility indices and the sperm parameters analyzed in vitro, to evaluate the relationship between sperm quality and the fecundity rate obtained by the bulls. Sperm kinetic parameters, including total motility, progressive motile, and beat cross-frequency, were higher in low fertility compared to high fertility bulls (P < 0.05). However, curvilinear velocity was greater in high fertility bulls followed by SS + TRT. Straight-line velocity, average path velocity, linearity, and beat cross-frequency beat were higher in high fertility bulls after SS + TRT. Reactive oxygen species was correlated with fertility after SS. In addition, there was a decrease in lipid peroxidation was observed only in high fertility bulls. However, lipid peroxidation and high fertility were correlated after PT and SS + TRT. The combination of in vitro sperm kinetic parameters predicted in vivo fertility more accurately than individual kinetic parameters. The lipid peroxidation of sperm is an important indicator of fertility in bulls. High fertility bulls appeared to be more susceptible to lipid peroxidation, which was only reduced in high fertility bulls, suggesting that their sperm can repair the damage induced by oxidative stress.

Synthesis and characterization of functionally graded SiC-mullite thermal material

SiC-mullite is considered for high temperature applications due to its high mechanical strength and thermal shock-resistance. However, maintaining these properties is challenged by the high processing temperature requirement for the formation and densification of the mullite phase which leads to abundant surface oxidation of SiC into cristobalite. Cristobalite has relatively poor mechanical strength and thermal properties compared to SiC. Herein, we report on using coal fly ash as a source of alumina (Al2O3) that reacts in situ with the silica (SiO2), oxidation product of SiC. The instantaneous mullite formation on the surface of SiC facilitated due to the presence of minor concentrations of metal oxides in coal fly ash, resulted in a strong bonding zone between the two phases at relatively low temperature. In this work, SiC was mixed with coal fly ash at weight ratios of 90SiC/10ash, 85SiC/15ash, 80SiC/20ash, and 75SiC/25ash and sintered at 1400 °C. Measurements of mechanical properties showed that the 85SiC/15ash composition had the highest mechanical strength among samples. XRD analysis showed the phase composition of thermally treated 85SiC/15ash to be 81.8 wt% SiC, 11.4 wt% mullite, and 6.8 wt% cristobalite. SEM-EDX revealed a concentration gradient of Al in the cristobalite which enhanced formation of functionally graded bonding zones between phases and resulted in SiC-mullite composite with high thermomechanical properties. The compressive strength, nanoindentation elastic modulus, and Vickers hardness were 434 ± 20 MPa, 370.9 ± 22.6 GPa, and 11.5 ± 1.2 GPa respectively. The thermal shock resistance test showed high dimensional and mechanical stabilities after quenching in liquid nitrogen (−196 °C) from 1400 °C. The SiC-mullite composite showed low thermal expansion co-efficient from 3.17 × 10−7/K to 5.615 × 10−6/K when the sample was heated from 182 K to 354 K. The specific heat capacity, thermal diffusivity, and thermal conductivity were 7.83 ± 0.0014 J/g.K, 1.04 ± 0.013 mm2/s, and 17 W/m.K at 100 °C, respectively. The SiC-mullite composite exhibited moderate electrical conductivity of 3.48 × 10−2 S/m at 1000 °C.

The Effect of Surface Roughness of Inconel 738 Superalloy on the Adhesive Properties of 8YSZ Coatings Deposited by Electrophoretic Deposition (EPD)

The electrophoretic deposition coating method has recently received attention as a new method for thermal barrier coating due to its advantages such as the simplicity of the method, controllability of the process, and the need for simple equipment. In this study 8 wt % yttria- stabilized zirconia was deposited on Inconel 738 substrate at room temperature by electrophoretic deposition. Before deposition, the substrates were treated by sand blasting treatment (by silica sands with different sizes) and roughness in the range of Ra=1 and Ra=3 was achieved on the substrate surfaces. The coated samples were sintered at 1100 °C temperature under controlled atmosphere (Ar atmosphere). X-Ray diffraction, scanning electron microscopy and thermal shock resistance technics were used to investigating of structural and phase properties and adhesiveness between coatings and substrates. Results from thermal shock resistance test show that by increasing roughness number, the thermal shock resistance ability first increased and then decreased. In addition, according to SEM images, increasing of roughness number, causes decrease the microcracks that creating in the coating surface. The best result was observed for coatings deposed on substrate with Ra=2.

Construction and corrosion behavior of Al2O3/Al2O3-Ca2SiO4 double ceramic coating

In this study, Al2O3/Al2O3-Ca2SiO4 powders was sprayed on stainless steel substrate which contains a nickel-chromium connecting layer. At the same time, Al2O3 coatings were produced by air-plasma-spraying technology as comparison. Anti-corrosion tests in acidic corrosive atmosphere, potentiodynamic polarization measurements and thermal shock resistance tests were carried out to evaluate the protection performance of coatings. The effects of inorganic sealing agent on the microstructure and properties of the coatings were studied. The results indicated that Al2O3/Al2O3-Ca2SiO4 double ceramic coating showed a better corrosion resistance, lower corrosion rate and a better thermal shock resistance than Al2O3 coating. The sealing treatment can improve the corrosion resistance of coatings while decreasing the thermal shock resistance dramatically.